Analysis of the structure, organization and sequence of nucleic acid molecules is important in the prediction, diagnosis and treatment of human disease and in the study of gene discovery, expression and development. One laboratory tool used in the analysis of nucleic acid molecules is the high density array (HDA). The HDA provides the framework for immobilization of biomolecules such as nucleic acid molecules for analysis on a rapid, large-scale basis. HDAs generally include a substrate having a large number of positionally distinct DNA probes attached to a surface of the substrate for subsequent hybridization to a DNA target.
The surfaces of both organic and inorganic substrates can be modified by the deposition of a polymeric monolayer coating or film to construct biomolecular assemblies. In addition, surface modification can also be used to promote adhesion and lubrication, modify the electrical and optical properties of the substrate surface, and create electroactive films suitable for various optical and electronic sensors and devices.
Compounds with amine functionality have been used in the preparation of surfaces for nucleic acid hybridization. Due to their ability to bond to a substrate with a hydroxyl group and their ability to bond to nucleic acids through an amine, silane compounds are useful as surface coatings that will effectively immobilize nucleic acids. One example of a silane used for biological assay preparation is gamma amino propyl silane (GAPS), which may be deposited by a variety of methods, including but not limited to, spin coating, spray coating and dip coating. GAPS slides provide a surface that immobilizes DNA through the non-covalent, electrostatic attachment to the slide surface. The GAPS molecule contains a single amine functionality and has a 3 carbon linker between the Si and the amine.
A very important consideration in the preparation of substrates for immobilization of biomolecules is uniformity of the substrate surface. It is important to provide uniform functionality over an extended area of the substrate. This is especially true in the case of high density arrays for performing biomolecular hybridization assays. Such assays rely on having uniform levels of biomolecule immobilization at known locations on the substrate. It is desirable to have substantially identically sized spots containing a known quantity of pre-determined set of capture biomolecules located on the substrate in a regular geometric array with low background or signal to noise. Ambiguous and/or erroneous readouts result from variations in the immobilization and localization of the capture biomolecules.
Although GAPS coated slides are widely used for the immobilization of biomolecules, it would be desirable to provide substrates with alternate surface modifications. It would be useful to provide substrate surface adapted for immobilization of biomolecules that could be modified to provide a wide variety of surface functionalities to provide flexibility in binding various biomolecules.